PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No neoadjuvant or postoperative adjuvant chemotherapy from 2 weeks before to 2 weeks after surgery Endocrine therapy: At least 4 weeks since prior somatostatin or somatostatin analogue No other concurrent somatostatin or somatostatin analogues Radiotherapy: No neoadjuvant or postoperative adjuvant radiotherapy from 2 weeks before to 2 weeks after surgery Surgery: See Disease Characteristics Other: No concurrent pancreatic enzyme inhibitors (e.g., antiproteases) No concurrent immunosuppressive agents